Ball-Milling-Induced Amorphization of Zeolitic Imidazolate Frameworks (ZIFs) for the Irreversible Trapping of Iodine

The I2‐sorption and ‐retention properties of several existing zeolitic imidazolate frameworks (ZIF‐4, ‐8, ‐69) and a novel framework, ZIF‐mnIm ([Zn(mnIm)2]; mnIm=4‐methyl‐5‐nitroimidazolate), have been characterised using microanalysis, thermogravimetric analysis and X‐ray diffraction. The topologically identical ZIF‐8 ([Zn(mIm)2]; mIm=2‐methylimidazolate) and ZIF‐mnIm display similar sorption abilities, though strikingly different guest‐retention behaviour upon heating. We discover that this guest retention is greatly enhanced upon facile amorphisation by ball milling, particularly in the case of ZIF‐mnIm, for which I2 loss is retarded by as much as 200 °C. It is anticipated that this general approach should be applicable to the wide range of available metal–organic framework‐type materials for the permanent storage of harmful guest species. Having a ball: The I2‐sorption and ‐retention properties of several zeolitic imidazolate frameworks have been characterised. The topologically identical ZIF‐8 ([Zn(mIm)2]; mIm=2‐methylimidazolate) and ZIF‐mnIm ([Zn(mnIm)2]; mnIm=4‐methyl‐5‐nitroimidazolate) display similar sorption abilities, though strikingly different guest‐retention behaviour (see figure). Upon facile amorphisation by ball milling, the guest retention is greatly enhanced.